On board a modern commercial aircraft there are provided a large number of components, for example electrical and electronic systems, which generate heat and therefore have to be cooled. Most aircraft cooling systems employed at present comprise air inlet openings, usually provided in the region of the aircraft outer skin, which can be formed as ram air inlets for example and serve to convey surrounding air as coolant into the aircraft cooling system. Cooling air, which is heated by absorbing heat from devices on board the aircraft which are to be cooled, is guided back into the surroundings generally through air outlet openings likewise provided in the region of the aircraft outer skin. The air inlet and air outlet openings formed in the aircraft outer skin, however, increase the aerodynamic drag and hence the fuel consumption of the aircraft. Moreover, aircraft cooling systems supplied with cooling air via ram air inlets have high pressure losses, a cooling capacity limited, inter alia, by the maximum supply air volume flow through the ram air inlets, and a relatively high weight.
Efforts are therefore being made to employ outer skin heat exchangers in aircraft cooling systems in order to remove heat from devices on board the aircraft which are to be cooled into the surroundings of the aircraft. DE 10 2008 026 536 A1, for example, describes a heat exchanger which is directly integrated into the aircraft outer skin, i.e. forms a section of the aircraft outer skin. By contrast, an arrangement is known from DE 10 2009 013 159 A1, in which a partial region of the aircraft outer skin is formed by cooling ribs through which surrounding air flows.
Finally, WO 2010/012684 A1 discloses a heat exchanger which is fastened to an inner surface or an outer surface of the aircraft outer skin and to which cool surrounding air is supplied through slits formed in the aircraft outer skin and extending parallel to a longitudinal axis of the aircraft. The surrounding air flows through cooling air ducts formed in the heat exchanger and in the process comes into thermal contact with fluid to be cooled which is guided through fluid ducts provided in the heat exchanger. The fluid ducts for the fluid to be cooled can be integrated, for example, into a plate, over which the cool surrounding air flows during the operation of the heat exchanger.